Natural Resources, 2012, 3, 75-87 Published Online September 2012 (
Raccoon Use of Den Trees and Plant Associations in
Western Mesophytic Forests: Tree Attributes and
Availability or Landscape Heterogeneity?
Winston P. Smith1,2, Keith M. Endres3
1United States Department of Agriculture, Forest Service, Southern Research Station, Center for Bottomland Hardwood Research,
Stoneville, USA; 2Institute of Arctic Biology, University of Alaska—Fairbanks, Fairbanks, USA; 3Department of Biology and Center
for Management, Utilization, and Protection of Water Resources, Tennessee Technological University, Cookeville, USA.
Received July 5th, 2012; revised August 13th, 2012; accepted August 22nd, 2012
We monitored 15 radio-collared raccoons (Procyon lotor) on Davies Island in March 1987-May 1988 to determine the
extent to which individual tree attributes or spatial configuration of plant associations (habitat types) across the land-
scape influenced den use. Of 1091 verified den sites, 428 were in tree cavities. Raccoon occurrence among 4 cover
types differed from that expected based on the total area of each across the island and varied across all seasons for all
habitat types except Cedar Wood. Preference varied among age and sex groups and across seasons with some groups
showing opposite selection for the same cover type in different seasons. Species and diameter-class distributions of se-
lected den trees differed from a random sample of trees across the landscape. Species composition of trees with cavities
also differed from the species composition across the study area. American beech (Fagus grandifolia—relative abun-
dance 8.7%) was over-represented in the sample of trees with cavities (29.4%) and trees selected as dens (65%); diame-
ter at breast height (dbh) of beech den trees averaged 80.0 cm, whereas all beech trees averaged 71.2 cm. For all species
combined, mean dbh of den trees was 78.4 cm as compared to trees with cavities (67.6 cm), or all trees (50.4 cm). The
relative availability of large, cavity-prone tree species was related to previous logging practices.
Keywords: Den Use; Habitat Use; Landscape Heterogeneity; Procyon lotor; Resource Availability; Mesophytic Forest
1. Introduction
The raccoon (Procyon lotor, Linnaeus) is common and
widespread across North America [1]. Despite having
earned a negative reputation in recent years because of its
ability to exploit human refuse and live in urban areas [2],
raccoons are still viewed as a desirable species in many
exurban areas. Raccoon hunting has a long history in the
Midwest and southeastern United States; an important
recreational activity that also contributed to the local
economy [3]. In natural communities, the raccoon is an
important predator of nesting waterfowl and other avian
species [4]. Its range is restricted largely by proximity to
water [5-7]. Some early investigators reported that
availability of suitable dens limited raccoon distribution
[8-12], but more recent studies have suggested den
availability was not a limiting factor [13-17].
Raccoons are opportunistic and use various types of
dens. In mixed-mesophytic forests, they used abandoned
squirrel nests, tree roosts, and barns in addition to the
well-documented rock and ground burrows and tree cavi-
ties [16,18]. Several studies reported raccoon preferences
for various den types, such as rock-outcroppings tree
cavities, and ground burrows [1,8,16,18-22]. Reference
[18] reported den selection varied among seasons and
age and sex groups.
Relative importance of dens in the hierarchy of resources
required by raccoons is uncertain, but likely varies across
seasons and among habitats and age and sex classes [18].
Whether trees selected as dens represent the best choice
(relative to reproductive fitness), or whether den selection
is secondary to raccoon preference for other resources
(e.g., food) within selected habitat types is unclear. In
spatially and temporally patchy environments, resources
often do not occur together and thus raccoons must make
choices relative to their needs and availability of resources
[18]. Moreover, broad-scale disturbance (e.g., logging)
can alter the availability and distribution of critical
resources [10].
Reference [18] quantified the use of a variety of den
types among four age-sex groups of raccoons in a closed
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
(i.e., island) population. The purpose of our study was to
examine use of tree dens relative to habitat type use by
raccoons in an extensively modified and heterogeneous
forested landscape. Specific objectives were to 1) quan-
tify features of den trees used by raccoons; 2) determine
if selection of den trees was correlated with habitat type
use; and 3) determine if variation in den use can be ex-
plained by den tree or habitat type availability.
2. Study Area
Our study area was Davies Island within Center Hill
Reservoir, DeKalb County, Tennessee (Latitude 36°00"
45'N, Longitude 85˚42"45'W). We conducted this study
on an island because it facilitated monitoring the move-
ments and behavior of an entire population that had re-
stricted access to a broader landscape [23]. Davies Island
is approximately (depending upon water level in Center
Hill Reservior) 2.20 km long (north to south) and 1.85
km wide and encompassed 271 ha. Topography is steep;
elevation ranged from 201 m above mean sea level at the
shoreline to 299 m on the highest ridge.
Seasonal temperature means for the region were as
follows: winter (December-February), 5.4˚C; spring (March-
May), 14.0˚C; summer (June-August), 24.2˚C; and au-
tumn (September-November), 15.0˚C [24]. Precipitation
was heaviest in winter, spring, and early summer, aver-
aging 137.2 cm annually. Frozen precipitation usually
occurred from November to May and averaged 20.8 cm
per year. Typically, snow cover was present for 4 - 9
days and the ground freezes to a depth of 10 cm.
Natural vegetation of the area is classified as Western
Mesophytic Forest [25], with different species assem-
blages depending on local site conditions. Reference
[26] described 4 upland plant communities on the island:
Beech/Maple; Oak/Hickory; Oldfield (Liriodendron-Ulmus-
Liquidambar); and Red-Cedar (=Cedar) woods. The can-
opy vegetation of Beech/Maple was characterized by the
dominance of American beech (Fagus grandifolia), and
maple species (Acer saccharum and A. rubrum). Under-
story vegetation consisted mostly of saplings of canopy
dominants, dogwood (Cornus florida), spicebush (Lin-
dera benzoin), and Eunoymous americanus. The herb
layer was comprised of dogtooth violet (Erythronium
americanum), dwarf crested iris (Iris cristata), phacelia
(Phacelia bipinnatifida), false Solomon’s seal (Smilacina
racemosa), Jack-in-the-Pulpit (Arisema triphyllum), and
maiden-hair fern (Adiantum pedatum). Canopy vegeta-
tion of Oak/Hickory was dominated by Quercus alba, Q.
falcate, Q. stellata, Carya glabra, C. ovalis, and C. ovata.
Understory vegetation consisted mostly of mountain lau-
rel (Kalmia latifolia), viburnum (Viburnum acerifolium),
and huckleberry (Vaccinium). The remaining species-
poor understory was comprised of xeric species, such as
spotted wintergreen (Chimaphila maculata), blood-
root (Sanguinaria canadensis), pennywort (Obolaria
virginica), christmas fern (Polystichum acrostichoides),
and beggar lice (Desmodium nudiflorum). Oldfield can-
opy was almost completely dominated by the tuliptree
(Liriodendron tulipifera), but included successional in-
dicators, such as black locust (Robinia psuedoacacia),
honey locust (Gleditsia triacanthos), tree-of-heaven (Ai-
lanthus altissima), butternut (Juglans cinerea), small elm
saplings (Ulmus rubra and U. thomasi), and sumac (Rhus
typhina). Understory vegetation consisted primarily of
saplings of canopy species and buckbush (Symphoricar-
pos orbiculatus). Herbaceous species reflected recent
disturbance and included thistle (Cirsium altissimum),
goldenrod (Solidago spp.), morning glory (Ipomea pan-
durata), dodder (Cuscuta gronovii), asters (Aster spp.),
wild sensitive plant (Cassia nictitans) and ragweed (Am-
brosia artemisiifolia). The Cedar Woods canopy was
exclusively dominated by red-cedar (Juniperus virgin-
iana), but included a few xeric species, such as Euphor-
bia corollata, E. dentate, E. mecurialina, Acalypha grac-
ilens, Ruellia ciliosa [26].
Davies Island had been managed by the US Army
Corps of Engineers since 1942 when it was acquired as
part of the Center Hill Reservoir development. Just prior
to its acquisition, the island underwent diameter-limit
(i.e., high-grade) harvests, which was a typical forestry
practice of non-industrial landowners throughout the
region [27]. The extensive, selective logging modified
the distribution and composition of natural vegetation
communities [25,26]. Since that time, the island has been
managed primarily for recreation with little vegetative
manipulation for either forest or wildlife management.
3. Materials and Methods
3.1. Capture, Handling and Monitoring Animals
We trapped raccoons using Havahart® (Woodstream
Corporation, Lititz, PA, USA) live traps (76.2 × 17.8 ×
17.8 cm) baited with sardines [18,28]. Captured raccoons
were immobilized with an intramuscular injection of a
mixture (9:1) of ketamine hydrochloride and acetyl pro-
mazine (0.2 cc/kg) [29,30] and fitted with collar-con-
figuration radio-transmitters (L2B5-H, Telonics, Mesa, AZ,
USA). Age of each animal was determined by comparing
tooth wear [31] with baculum length and nipple size [32].
Animals <14 months of age (age class I) were catego-
rized as juveniles; older animals (age classes II - V) were
grouped into a single adult category.
We monitored radio-collared raccoons from March
1987 to May 1988 using a rotating, systematic sampling
schedule [18]. At least 3 times weekly, each study animal
was located during 1 of 6 circadian activity periods de-
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Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
fined according to sunrise and sunset: early morning, late
morning, early afternoon, late afternoon, early evening,
and late evening. Additional observations of each rac-
coon were recorded in the remaining activity periods so
that during each calendar season we recorded a minimum
of 24 locations per animal distributed evenly among all
activity periods. This procedure was repeated for all sea-
sons throughout the study period. Observations of indi-
viduals accompanied by 1 additional raccoons were
treated as a single, independent, observation. This scheme
minimized the potential problem of non-independence of
observations in analyses of resource selection [33]. In our
paper, tree den was defined as a cavity in the bole or
large branch of a tree that provided shelter from inclem-
ent weather and predators (including hunting dogs), es-
pecially for females nursing young [10,20].
Den locations were verified by walking toward each
individual following initial triangulation and identifying
den trees or habitat type according to intensity and qual-
ity of the radio-transmitter signal [18]. Locations were
recorded on individual aerial photographs (scale: 1:5000)
and then transferred to a contour map of the island that
was digitized from a U.S.G.S. topographic map into
ARC/INFO (Environmental Systems Research Institute,
Inc., Redlands, CA). Date, time, activity (e.g., denning),
and habitat type were recorded.
3.2. Vegetative Sampling and Statistical Analysis
We used relative abundance of trees with suitable cavity
openings (i.e., appeared large enough to accommodate
raccoons) [28] to reflect the availability of tree species
among diameter classes. We used a stratified, random-
systematic sampling procedure [34] to establish 103 point-
center quarter sampling points [35]. That is, proportion-
ally among habitat types we randomly selected the cen-
tral point in a plot from which additional sampling points
were systematically determined [35]. The variance and
effect sizes in a preliminary sample indicated we needed
100 points [28] to discern differences between available
and used trees. We determined frequency, species com-
position, density and diameter-at-breast height (dbh) for
tree stems >l-m circumference and recorded whether
there were suitable cavities. Although raccoons may den
in smaller trees, our preliminary sample indicated that
trees that were <l-m circumference (i.e., <32 cm dbh)
rarely had visible cavities, or the cavities appeared too
small to be used by raccoons. We stratified tree data
among 5-cm diameter classes and used Kolmogorov-
Smirnov two-sample tests (NPAR1WAY, SAS/STAT
User’s Guide) [36] to assess whether the species fre-
quency distribution of trees with cavities or trees selected
as dens differed from that available across the island [37].
A similar test for continuous data [37] compared the dbh
frequency distribution of cavity trees or den trees with
the expected distribution.
We used ARC/INFO to develop an island-wide cov-
erage of plant associations (hereafter habitat types) from
recent satellite imagery and aerial photographs (Figure
1). Vegetation sampling and ground-truthing established
and verified plant associations (hereafter habitat type)
across the landscape, respectively. Proportion of the is-
land encompassed by each habitat type was used to esti-
mate its availability to raccoons. We also used ARC/
INFO to obtain relative abundance of habitat types
within seasonal and annual convex polygon home ranges
[38] of each study animal. We compared those to corre-
sponding habitat type proportions across the entire island
as an assessment of landscape-scale selection of habitat
types by individual raccoons. Comparison of relative use
(pi) of each habitat type (i.e., proportion in an individu-
als’ home range) with its corresponding availability, i.e.,
relative abundance (po) across the island, determined
habitat type preference [39].
We used multiple contingency table analyses [36] to
determine if significant variation in habitat type selection
occurred among seasons or among age and sex groups
[37]. We used Log-Likelihood Ratio for Contingency
Tables (G-statistic) when individual cells had expected
values that were <5. We used partial chi-square analysis
to determine if significant interaction between variables
occurred and which categories differed [37]. Selection
occurred when raccoon use of a resource differed statis-
tically from what was expected based on the relative
abundance (i.e., availability) of each possible category
(e.g., tree species); preference refers to use that is greater
than expected, whereas avoidance is use that is less than
expected. A probability of 0.05 was accepted as indicat-
ing statistical significance.
Convex polygon estimates of home range can be sub-
ject to a sample size bias [40]. However, we estimated
the minimum sample size beyond which home range
Figure 1. Davies Island, Center Hill Reservoir, USA.
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
increased negligibly by plotting number of locations
against home-range size [41]. Only raccoons with 20
independent observations during a season or 30 inde-
pendent observations over 9 months during a year were
included in corresponding analyses. Also, we assumed
that we had sufficient statistical power to discern differ-
ences between habitats used relative to availability [33].
Because we recorded markedly fewer observations in
some season × sex × age categories, there may have been
a higher likelihood of a Type II error in multiple com-
parisons of use versus availability. However, there was
clear evidence of significant habitat type selection in all
but one of the 16 categories we examined; and the cate-
gory without any evidence of selection had as many or
more observations than most of the remaining categories.
Conversely, it is possible that pooling observations
(rather than analyzing observations of each animal sepa-
rately) reduced individual variation and inflated degrees
of freedom, a consequence of which might have been
over-sensitive statistical analyses resulting in an inflated
Type I error [42]. However, we pooled observations only
according to age-sex groups, which we expected to be-
have similarly because of similar life history needs [18];
pooling data across animals is justifiable when they do
not differ [42]. Also, because degrees of freedom of our
initial Chi-square analysis to compare use with availabil-
ity was based on number of groups (not number of ob-
servations) [37], we believe the Type I error was not in-
flated. Still, it is possible to obtain spurious conclusions
about resource selection if the assumption that individu-
als within age-sex group behave similarly is untenable.
Finally, we assumed that the relative amount of each
habitat type across the study area was a realistic estimate
of its availability. Reference [43] pointed out that be-
cause of the selective nature of many animals, the entire
area of each habitat might not be available. Because of
topography, geology, and land use, the landscape across
our study area was heterogeneous; habitat types and
other resources were patchily distributed across the is-
land. Nonetheless, we believe that total area of each
habitat type was probably a good estimate of availability
because telemetry data indicated that individual raccoons
could readily travel to any part of the island [18].
4. Results
We captured and fitted 15 raccoons with radio-transmit-
ters during March-September 1987 and monitored each
through April 1988: 4 male and 3 female juveniles, and 4
male and 4 female adults. We recorded 1231 daytime and
607 nighttime observations during March 1987-May
1988, from which we obtained 1665 independent obser-
vations of habitat type use. Of the daytime locations,
1091 were verified and all but 15 observations were
designated as den use by a single raccoon. On 428
(39.2%) occasions, raccoons selected tree cavities for
denning; remaining den sites were either ground burrows
or grottos within rock out-croppings.
4.1. Habitat Avail a bi l it y a n d Use
4.1.1. Habitat Selection across the Landscape
Beech/Maple forest occurred throughout most of the
study area and was the most abundant habitat type, rep-
resenting about 59.2% (160.4 ha) of the island (Figure 1).
Oak/Hickory forest was the next most abundant plant
community, occupying 78.9 ha (29.1%), but mostly re-
stricted to the eastern and southern edge of the island.
Cedar Woods (7.7%) and Oldfield (4.0%) communities
comprised the remaining 31.7 ha; Oldfield was limited
(>75% of the total) to the northwest quarter of the island,
whereas Cedar Woods occurred along the east-and west-
central edges of the study area (Figure 1).
Mean proportion of each habitat type included in sea-
sonal home ranges of radio-collared raccoons (Table 1)
differed (spring –χ2 = 676, df = 3, P < 0.001; summer –χ2
= 225, df = 3, P < 0.001; autumn –χ2 = 552, df = 3, P <
0.001; winter –χ2 = 808, df = 3, P < 0.001) from what
was expected based on the total area of each habitat type
across the study area. Annual averages were as follows:
Beech/Maple forest, 70.5%; Oak/Hickory forest, 13.1%;
Cedar Woods, 10.0%; and Oldfield, 6.4%. Invariably,
Beech/Maple forest was a greater percentage and Oak/
Hickory a smaller proportion of seasonal home ranges
than expected from their representation across the island
(Table 1). Remaining habitat types were less predictable,
varying both among seasons and according to the age and
sex of individuals. Mean proportion of habitat types
within seasonal home ranges did not vary among seasons
(χ2 = 8, df = 12, P > 0.50).
4.1.2. Habitat Use within Home Ranges
According to radio-telemetry locations within home
ranges, raccoon use of habitat types was not independent
of season (χ2= 113, df = 9, P < 0.0001) or age and sex
group (χ2 = 373, df = 9, P < 0.0001). Generally, habitat-
type use differed (P 0.05) among all seasons for all
habitat types; an exception was Cedar Woods, in which
there was proportional use (χ2 < 7.815, df = 3, P > 0.05)
throughout the year (Table 1). The greatest departure
from uniform use among seasons occurred during sum-
mer for all habitat types except Cedar Woods, use of
which deviated during autumn. Raccoons used Beech/
Maple and Oak/Hickory more during spring and less
during summer than expected (Table 2). In contrast,
Oldfield received greater use during summer and less use
during spring than expected.
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
Copyright © 2012 SciRes. NR
Table 1. Average proportions of habitat types in seasonal home ranges of raccoons (Procyon lotor) (n = 15) and mean per-
centage of radio-telemetry locations recorded within each habitat type, Davies Island, Center Hill Reservoir, Tennessee, USA,
March 1987-May 1988. (Range is given in parentheses).
Type of Observation Beech-Maple (%) Oak-Hickory (%) Cedar Woods (%) Oldfield (%)
Home Range Composition 77.1 (66.1 - 96.7) 10.6 (0.0 - 28.5) 5.4 (0.1 - 14.9) 6.8 (0.0 - 18.6)
Telemetry Locations 65.1 (60.6 - 70.3) 10.5 (0.0 - 16.2) 12.6 (4.3 - 19.0) 11.8 (0.0 - 30.3)
Home Range Composition 64.4 (38.4 - 79.4) 16.2 (0.0 - 51.2) 11.7 (3.1 - 22.8) 7.9 (0.1 - 21.4)
Telemetry Locations 37.2 (23.8 - 55.0) 24.9 (0.0 - 39.1) 11.2 (6.2 - 16.2) 26.7 (10.8 - 53.6)
Home Range Composition 75.0 (58.9 - 84.7) 11.9 (0.0 - 32.0) 6.8 (3.3 - 21.3) 6.3 (0.1 - 15.9)
Telemetry Locations 55.8 (41.5 - 80.9) 17.8 (0.0 - 44.6) 6.6 (3.1 - 8.0) 19.8 (1.4 - 47.1)
Wi nter
Home Range Composition 77.9 (56.2 - 99.9) 7.8 (0.0 - 36.8) 8.5 (0.0 - 32.8) 6.1 (0.1 - 21.4)
Telemetry Locations 62.7 (47.2 - 77.7) 14.2 (0.0 - 36.5) 13.2 (1.9 - 30.1) 9.9 (0.0 - 22.3)
Table 2. Seasonal occurrence of juvenile and adult female and male raccoons (Procyon lotor) among habitat types March
1987-May 1988; n = number of locations and used to compute family confidence intervals [39].
Spring (n = 456)
Males (n = 159)
Juveniles (n = 42) Adults (n = 117)
Habitat types Proportion of all
habitat typesa (po)
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.667 0.486 - 0.848 o 0.624 0.512 - 0.736 o
Oak/Hickory 0.291 0.143 0.008 - 0.278 o 0.162 0.077 - 0.247 -
Cedar Woods 0.077 0.190 0.039 - 0.341 o 0.043 0.000 - 0.090 o
Oldfield 0.040 0.000 0.000 - 0.000 - 0.171 0.084 - 0.254 +
Females (n = 297)
Juveniles (n = 132) Adults (n = 165)
Habitat types Proportion of all
habitat typesa (po)
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.606 0.500 - 0.712 o 0.703 0.614 - 0.792 +
Oak/Hickory 0.291 0.000 0.000 - 0.000 - 0.115 0.053 - 0.177 -
Cedar Woods 0.077 0.091 0.028 - 0.154 o 0.182 0.107 - 0.257 +
Oldfield 0.040 0.303 0.203 - 0.403 + 0.000 0.000 - 0.000 -
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
Summer (n = 426)
Males (n = 194)
Juveniles (n = 130) Adults (n = 64)
Habitat types Proportion of all
habitat typesa (po) Proportion
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.238 0.145 - 0.331 - 0.359 0.209 - 0.509 -
Oak/Hickory 0.291 0.362 0.302 - 0.422 + 0.391 0.239 - 0.543 o
Cedar Woods 0.077 0.162 0.081 - 0.243 + 0.062 0.000 - 0.137 o
Oldfield 0.040 0.238 0.145 - 0.331 + 0.188 0.066 - 0.310 +
Females (n = 232)
Juveniles (n = 112) Adults (n = 120)
Habitat types Proportion of all
habitat typesa (po)Proportion
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.339 0.227 - 0.451 - 0.550 0.437 - 0.663 o
Oak/Hickory 0.291 0.000 0.000 - 0.000 - 0.242 0.144 - 0.340 o
Cedar Woods 0.077 0.125 0.047 - 0.023 o 0.100 0.032 - 0.168 o
Oldfield 0.040 0.536 0.418 - 0.654 + 0.108 0.037 - 0.179 o
Autumn (n = 443)
Males (n = 169)
Juveniles (n = 104) Adults (n = 65)
Habitat types Proportion of all
habitat typesa (po)
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.558 0.436 - 0.680 o 0.415 0.262 - 0.568 -
Oak/Hickory 0.291 0.164 0.073 - 0.255 - 0.446 0.292 - 0.600 +
Cedar Woods 0.077 0.077 0.012 - 0.142 o 0.031 0.000 - 0.085 o
Oldfield 0.040 0.201 0.103 - 0.299 + 0.108 0.012 - 0.204 o
Females (n = 274)
Juveniles (n = 138) Adults (n =136)
Habitat types Proportion of all
habitat typesa (po)
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.449 0.343 - 0.555 - 0.809 0.725 - 0.893 +
Oak/Hickory 0.291 0.000 0.000 - 0.000 - 0.103 0.038 - 0.168 -
Cedar Woods 0.077 0.080 0.022 - 0.138 o 0.074 0.018 - 0.130 o
Oldfield 0.040 0.471 0.356 - 0.577 + 0.014 0.000 - 0.039 -
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
Copyright © 2012 SciRes. NR
Winter (n = 340)
Males (n = 134)
Juveniles (n = 71) Adults (n = 63)
Habitat types Proportion of all
habitat typesa (po)
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.746 0.617 - 0.875 + 0.508 0.351 - 0.665 o
Oak/Hickory 0.291 0.000 0.000 - 0.000 - 0.365 0.214 - 0.516 o
Cedar Woods 0.077 0.099 0.011 - 0.187 o 0.111 0.012 - 0.210 o
Oldfield 0.040 0.155 0.048 - 0.262 + 0.016 0.000 - 0.055 o
Females (n = 206)
Juveniles (n = 103) Adults (n = 103)
Habitat types Proportion of all
habitat typesa (po)
observed (pi)
95% family confidence
interval for pib Index of usecProportion
observed (pi)
95% family confidence
interval for pib Index of usec
Beech/Maple 0.592 0.472 0.349 - 0.595 o 0.777 0.675 - 0.879 +
Oak/Hickory 0.291 0.000 0.000 - 0.000 - 0.204 0.105 - 0.303 o
Cedar Woods 0.077 0.301 0.188 - 0.414 + 0.019 0.000 - 0.053 -
Oldfield 0.040 0.223 0.121 - 0.325 + 0.000 0.000 - 0.000 -
aProportions of all den types represent availability and expected raccoon use of each corresponding den type; bIndividual den-type proportion estimates repre-
sent 98.5% (α/2k) confidence intervals [39]; c+ = preferred, - = avoided, o = used in proportion to availability.
4.1.3. Habitat Use Relative to Availability
Overall, raccoon occurrence within habitat types differed
(χ2 = 2,379, df = 27, P < 0.0001) from that expected ac-
cording to the relative abundance of each across the is-
land (Table 2). Two exceptions were male and female
adults during winter and summer, respectively. Moreover,
use of habitat types relative to availability varied accord-
ing to individual age and sex and among seasons. Adult
females avoided (P < 0.05) Oldfield during all seasons,
except summer, when it was used proportionally. In con-
trast, juvenile females preferred Oldfield throughout the
year. In addition, there were circumstances in which the
same individuals exhibited diametrically opposite selec-
tion for the same habitat type in different seasons. Juve-
nile males used Beech/Maple forest much less than ex-
pected during summer, but preferred (P < 0.05) this
habitat type during winter. A similar pattern occurred
with juvenile male use of Oak/Hickory forest during au-
tumn and summer, respectively (Table 2).
Beech/Maple forest (the most abundant habitat type)
was mostly avoided or used proportionally. Adult fe-
males, however, frequently used Beech/Maple through
out the year with strong preferences during spring and
autumn (Table 2). Conversely, Oldfield (the least abun-
dant habitat type) received greater use than expected
during at least 2 seasons by all raccoons. During summer,
Oldfield was preferred by all raccoons except adult fe-
males, whose use approached statistical significance
(Table 2). Oak/Hickory forest was preferred by juvenile
and adult males during summer and autumn, respectively,
but mostly avoided by females, receiving only propor-
tional use by adult females during summer and winter.
With few exceptions, Cedar Woods was used propor-
tionally throughout the year by all raccoons.
4.2. Den Tree Availability and Use
We assessed availability of cavity openings in 412 trees
representing 28 species. Species for which there was only
a single observation (n = 7) were pooled into a single
category entitled “Other” (Table 3). A total of 41 trees
distributed among 12 species had 1 visible cavity open-
ing large enough to accommodate raccoons. The sample
of trees selected as dens consisted of 109 individual trees
and 10 species (Table 3). Mean dbh of available trees
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
ranged from 36.9 to 71.2 cm and averaged 50.4 cm (Ta-
ble 3). Overall, trees with cavities averaged 67.6 cm
(range 34.7 - 101.9), whereas den trees averaged 78.4 cm
(range = 39.1 - 109.2). The density of trees with >l-m
circumference was 77.6 stems/ha; trees with visible cavi-
ties averaged 8.1 stems/ha.
4.2.1. S p ec ies Compo s ition of A va ilable and Selected
Den Trees
Relative frequency of each species among trees with
cavities differed (D = 0.773, P = 0.0001) from that pre-
dicted by each species representation among trees with
>l-m circumference across the island (Figures 2(a) and
(b)). Also, species composition of trees selected as dens
(Figure 2(c)) differed (D = 0.773, P = 0.0001) from the
forest stand composition (Figure 2(a)), but did not differ
(D = 0.227, P = 0.621) from the sample of trees with
cavities (Figure 2(b)).
Most cavities (67%) occurred among 3 species (Fig-
ure 2(b)). American beech was over-represented in the
distribution of trees with cavities (34.9%; Figure 2(b))
and in the sample of trees selected as dens (65%; Figure
2(c)) as compared to its representation across the island
(8.7%; Figure 2(a)). In addition, sugar maple (Acer sac-
charum) and bitternut hickory (Carya cordiformis) com-
prised a greater proportion of trees with cavities than
expected. Among den trees, yellow poplar (Liriodendron
tulipfera) represented the second-most frequently se-
lected species, but it represented 34% of available trees
across the island (Figure 2(a)). White oak (Quercus
alba), however, was selected 4× more often than ex-
Table 3. For stems > l-m circumference, frequency, and mean diameter-at-breast height (cm) of available trees, trees with
cavities, and trees used by raccoons (Procyon lotor) for denning on Davies Island, Center Hill Reservoir, Tennessee, March
1987-May 1988. (n = sample size; s = standard deviation).
Available Trees with Cavities Den Trees
Species Mean s n Mean s n Mean s n
Liriodendron tulipifera 45.6 0.408 140 58.9 0.661 3 65.0 13.053 13
Fagus grandifolia 71.2 0.554 36 79.3 0.549 15 80.0 17.336 71
Quercus prinus 49.9 0.529 31 101.9 0 1 73.7 16.343 5
Acer saccharum 50.6 0.458 30 57.6 0.628 8 - - -
Quercus rubra 59.7 0.728 26 69.4 0.481 2 109.2 0 1
Carya cordiformis 53.3 0.608 23 62.0 0.681 6 - - -
Carya ovata 46.6 0.360 18 50.8 0 1 50.8 0 1
Fraxinus americana 45.8 0.315 18 74.2 0 1 95.5 0 1
Liquidambar styraciflua 42.0 0.268 16 - - - 39.1 0 1
Quercus alba 53.0 0.467 12 - - - 85.1 17.400 13
Quercus muehlenbergii 43.4 0.235 10 56.0 0 1 - - -
Acer rubra 54.1 0.731 7 95.5 0 1 - - -
Aesculus octandra 38.9 0.235 7 36.0 0 1 - - -
Quercus coccinea 57.1 0.644 7 - - - - - -
Juniperus virginiana 56.8 0.187 6 - - - - - -
Ailanthus altissima 41.2 0.248 6 34.7 0 1 - - -
Platanus occidentalis 54.6 0.577 3 - - - 83.8 0 2
Prunus serotina 42.5 0.346 3 - - - - - -
Carya tomentosa 78.8 0.247 2 - - - - - -
Diospyros virginiana 36.9 0.212 2 - - - - - -
Tilia heterophylla 52.5 0.240 2 - - - - - -
Other 41.5 0.226 7 37.2a 0 1 87.6b 0 1
Total 412 41 109
aQuercus ilicifolia; bUlmus americana.
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
Figure 2. Relative frequency distribution of trees among
species that comprised potential (stems >1-m circumference)
cavity trees (a); trees with cavities large enough to ac-
commodate raccoons (b); and trees selected as dens by rac-
coons (c); Davies Island, Center Hill Reservoir, Tennessee,
USA, March 1987-May 1988.
4.2.2. Diameter Distribution of Available and Used
Den Trees
The relative frequency of trees with cavities (D = 0.545,
P = 0.003) and den trees (D = 0.489, P = 0.01) among
5-cm diameter classes departed from the expected forest
stand composition (Figure 3). The diameter distribution
of den trees, however, did not differ from available trees
with cavities (D = 0.364, P = 0.109). Most (72.4%)
available trees were in diameter classes ranging from
30.0 to 60 cm (Figure 3(a)), whereas 72.5% of den trees
were in diameter classes ranging from 65 cm to 100 cm
(Figure 3(c)). Similarly, most (51.2%) available trees
with cavities (Figure 3(b)) were in diameter classes be-
tween 60 cm and 90 cm. For all species combined, mean
dbh of trees differed among categories (F = 8.89, df = 2,
562, P < 0.0001; one-way ANOVA) [37]. Potential trees
Figure 3. Relative frequency distribution of trees among
diameter classes that comprised potential (stems >1-m cir-
cumference) cavity trees (a); trees with cavities that were
large enough to accommodate raccoons (b); and trees se-
lected as dens by raccoons (c); Davies Island, Center Hill
Reservoir, Tennessee, USA, March 1987-May 1988.
(mean = 50.4 cm) were smaller (q = 7.41, df = 562, k = 3,
P < 0.001, Tukey test) [37] than den trees (mean = 78.4
cm) and smaller (q = 4.99, df = 562, k = 3, P < 0.005)
than trees with cavities (mean = 67.6 cm); den trees did
not differ from trees with cavities (q = 2.66, df = 562, k =
3, P > 0.10).
5. Discussion
5.1. Habitat Selection
Habitat-type selection was estimated at two spatial scales:
the proportion of habitat types in individual home ranges
likely reflected choices made relative to what was avail-
able across the entire island; whereas, radio-telemetry
locations represented more fine-scale habitat selection
within home ranges [43]. The overall similarity between
spatial scales in relative use of habitat types among sea-
sons suggests that attractive micro- and macro-habitat
features were not spatially segregated [44]. Notable ex-
ceptions were Beech/Maple forest and Oldfield during
summer when each comprised a larger and smaller por-
tion, respectively, of raccoon home ranges than corre-
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
sponding estimates of habitat-type use obtained from
telemetry locations. However, raccoon home ranges in-
cluded Beech/Maple sites that were adjacent to Oldfield,
which were visited frequently during summer.
Raccoons in this study showed substantial variation in
use of habitat types. Seasonal variation was likely asso-
ciated with temporal and spatial heterogeneity of resources
[45]. Raccoons on the island exhibited little home range
fidelity among seasons [28]; frequently, movements were
directly associated with seasonal and patchy food re-
sources such as Rubus sp., Vitis sp, and Diospyros sp.
[18]. A similar shift in center of activity relative to
availability of ephemeral food resources has been re-
ported by several investigators [1,46-48]. Furthermore,
the response of individuals to patchy resource distribu-
tion varies significantly among raccoons of different age
and sex [18,49].
In this study, resources varied both spatially and tem-
porally. Oldfield and Cedar Woods did not occur on a
large portion of the island. Also, distributions of potential
cavity trees were not uniform throughout the island.
Bitternut hickory, in particular, occurred less in the
southern portion and was more common in the central
portion of the island. Select food resources such as Rubus
sp. were available solely at certain times of the year and
occurred mostly in Oldfield. Raccoons responded to
ephemeral resources by concentrating activity within
those areas. Reference [44] reported similar behavior,
noting that raspberries frequently influenced fine-scale
raccoon activities and use of associated or adjacent habi-
tats. In our study, the preference by essentially all rac-
coons for Oldfield throughout the summer was likely
related to an abundance of blackberries [18].
Because raccoons often establish den sites near con-
centrated food sources [18,22,46,49], frequent activity
surrounding blackberry thickets in this study likely had
implications for other resources. Certain habitat types or
other resources likely were used more or less depending
upon juxtaposition to Oldfield. It was not uncommon to
observe several raccoons use less preferred den trees
(e.g., sweetgum, or smaller oaks) while using blackberry
thickets in the same Oldfield patch. Reference [44] re-
ported that raccoon use of certain microhabitat features
or fine-scale resources was significantly influenced by
the broader landscape context. They noted that raccoons
were more likely to use suboptimal habitats in portions of
landscapes with large amounts of other preferred re-
Raccoons in this study substantially reduced their use
of Beech/Maple during summer; only adult females did
not avoid this habitat type. There were Beech/Maple
stands immediately adjacent to most of the Oldfield
patches on the island. To most raccoons, a change in use
of Beech/Maple during summer likely was a cones-
quence of their increased use of Oldfield; that is, rac-
coons likely were responding to the positive value of
Rubus thickets. To females with young, however, the
coincidence of Oldfield and Beech/Maple likely repre-
sented an especially attractive condition. Cavities in large
American beech trees probably were an equally valuable
resource to females with young [10] that facilitated ac-
cess to an essential, temporary food resource without
compromising the quality of natal dens. This conclusion
is supported by several lines of evidence. First, females
with young mostly used American beech for denning
during this period, whereas other raccoons used ground
burrow dens in the immediate vicinity of Rubus thickets
[18]. Second, summer home ranges of adult females were
comprised largely of Beech/Maple stands near Oldfield,
the latter of which experienced as much use as the former
yet represented a much smaller portion of the home range.
Third, adult females used Beech/Maple forest more often
than males during summer. Fourth, Oldfield and adjacent
Oak/Hickory stands on the southwestern portion of the
island received little use by females during this period.
Finally, excluding adult females, Oak/Hickory stands
were apparently attractive to most raccoons during sum-
mer. Indeed, juvenile males preferred this habitat type,
spending most of the summer in Oak/Hickory forest.
Some of the significant variation in this study cannot
readily be explained as it does not seem consistent with
our understanding of raccoon behavior. Oak/Hickory
occurred over nearly 30% of the island, yet received less
than 16% use overall. This may in part be due to its
availability in the home ranges of individuals that se-
lected other portions of the landscape. Regardless, rac-
coons were avoiding either Oak/Hickory or the eastern
and southern edge of the island. Some raccoons (e.g.,
adult males) preferred Oak/Hickory during some seasons;
others (e.g., juvenile females) were never recorded in
Oak/Hickory. We expected more general use of this
habitat type, especially during autumn when fruits and
nuts typically are an abundant food resource. Mean den-
sity of hard and soft fruit-bearing trees >32 cm dbh was
32 stems/ha. Hickories and oaks comprised 76% (24
stems/ha) of the mast-producing trees with red oak
(Quercus rubra), white oak (Q. alba) and shagbark hick-
ory (Carya ovata) averaging 4.9, 2.3 and 3.4 stems/ha,
Reference [50] recommended a minimum of 56 stems/
ha of oaks and hickories >25 cm dbh to meet the needs of
squirrels in mixed hardwood forests. Although raccoons
probably do not depend as heavily on hard mast as tree
squirrels (Sciuridae), it appears that the abundance of
desirable mast-producing trees on Davies Island was ap-
preciably less than would be considered minimally ade-
Copyright © 2012 SciRes. NR
Raccoon Use of Den Trees and Plant Associations in Western Mesophytic Forests:
Tree Attributes and Availability or Landscape Heterogeneity?
quate for supporting some arboreal species [50]. Unfor-
tunately, we did not collect any data on acorn or other
fruit production during this study. A study by [51], how-
ever, suggests that acorn production on Davies Island
should have been adequate. Mean diameter of red oaks
and white oaks on Davies Island (Table 3) approached
bole sizes of oak trees that typically produce most often
and yield the greatest quantity of acorns [51].
5.2. Den Tree Selection
Trees with cavities clearly were larger and biased toward
just a few species. Similar results were reported for an
Oak/Hickory forest in Missouri [52] and among several
forest types in South Carolina and Florida [53]. Raccoons
in our study selected the largest cavity trees as den trees,
most of which were American beech, a species that is
cavity-prone on many hardwood sites [50,54]. Reference
[10] reported an even greater bias (91%) towards
American beech as a den tree.
The relative importance of den sites, food, or other
resources as priorities influencing raccoon habitat se-
lection varies among seasons and age and sex groups
[18]. Some raccoons apparently are more flexible and
can adapt to varying circumstances. Reference [55] re-
ported raccoons will travel relatively long distances
between concentrated food resources and daytime den
sites. However, the scale (temporal or spatial) at which
resources are distributed influences the process of habitat
selection, with selection of food resources typically
occurring at fine spatial scales and landscape structure
and patterns at broader scales influencing selection of
macrohabitats comprising home ranges [45]. Most rac-
coons in our study area reduced their use of tree cavities and
chose to use nearby burrows when responding to highly
desirable ephemeral food resources [18]. For females
with young, however, the availability of nearby cavities
for denning may be crucial for successful reproduction
with consequences for the entire population.
Landscape heterogeneity influences the extent to
which desirable fine-scale resources and preferred macro-
habitats occur coincidentally and thus ultimately deter-
mines whether individuals must make trade-offs when
selecting resources [45]. Broad-scale disturbances con-
tribute to landscape heterogeneity by modifying the spe-
cies composition and structural characteristics of vegeta-
tion communities within and among habitat types [26].
Although many hardwood forests in the southeastern
United States are managed to achieve wildlife habitat
restoration, this may require complete removal of the
existing canopy on previously logged forests (especially
on public lands). Our results suggest that removal of
large-diameter stems across large areas could impact
arboreal species or other wildlife that depend on cavities
for denning. To ensure that wildlife populations that de-
pend on cavities or other attributes of large deciduous
trees are not locally extirpated, we encourage managers
to consider retaining large-diameter stems within or near
harvested sites (e.g., streamside management zones or
other unharvested areas).
6. Conclusions
Resource selection by raccoons can be significantly in-
fluenced by several proximate factors. Moreover, infer-
ences regarding selection of resources may vary, and
even appear conflicting, when examined at different spa-
tial scales and preferred resources are spatially segre-
gated. Sorting out meaningful and useful generalizations
becomes even more difficult when individuals within
populations exhibit different priorities in selecting re-
sources. We caution generalizing specific values or dif-
ferences reported in this study because of the small
number of raccoons represented in some analyses. Still,
the significant differences and patterns we report likely
indicate meaningful biological variation that warrants
some consideration in land-use or conservation planning.
An additional contribution of our findings is recogni-
tion that all raccoons are not identical in their immediate
needs or behaviors related to resource selection and sig-
nificant components of that dissimilarity are seasonal and
attributable to age and sex of individuals. What most
raccoons choose to do most of the time in different eco-
logical circumstances may not be as important in consid-
ering management options as whether crucial resources
are coincidentally available to a relatively few individu-
als during a narrow window of time to facilitate success-
ful reproduction. Thus, the question posed by the title of
this paper identifies a key challenge facing land manag-
ers today and in the future. That is, how do we manage
hardwood forests so that habitat use is not a compromise
in selection of fine-scale resources because of constraints
imposed by landscape configurations?
7. Acknowledgements
We thank the Tennessee Wildlife Resources Agency and
Tech Aqua, College of Arts and Sciences, Tennessee
Technological University for supporting this study. J. M.
Benner, D. L Borden, and J. H. McGuiness helped with
various aspects of the study. Beverly Collins reviewed an
early draft of this manuscript and provided valuable
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